Without limiting the scope of the present invention, its background is described with reference to using optical fibers for communication in a subterranean wellbore environment, as an example. It is well known in the subterranean well completion and production arts that downhole sensors can be used to monitor a variety of parameters in the wellbore environment. For example, during a treatment operation, it may be desirable to monitor a variety of properties of the treatment fluid such as viscosity, temperature, pressure, velocity, specific gravity, conductivity, fluid composition and the like. Transmission of this information to the surface in real-time or near real-time allows the operators to modify or optimize such treatment operations to improve the completion process. One way to transmit this information to the surface is through the use of communication lines, such as one or more optical fibers, copper or metallic cables, or hydraulic or pressure lines. In addition, optical fibers may serve as sensors, where the optical fiber obtains distributed measurements related to a parameter along the length of the fiber.
In a typical wellbore treating or stimulation operation, a lower portion of completion string including various tools such as sand control screens, fluid flow control devices, wellbore isolation devices and the like is permanently installed in the wellbore. The lower portion of the completion string may include various sensors, particularly, a lower portion of optical fiber. After the stimulation process, an upper portion of the work string including an upper portion of optical fiber is separated from the lower completion string and retrieved to the surface. This operation cuts-off communication between the lower string, which remains in place, and the surface. Accordingly, if information from the production zones is to be transmitted to the surface during later production operations, a connection to the lower optical fiber must be reestablished when the production tubing string is installed.
It has been found, however, that wet-mating optical fibers in a downhole environment is very difficult. Difficulties due to lack of precision in the axial movement of the production string relative to the previously installed completion string are addressed, for example, in U.S. Pat. No. 8,122,967, to Richards, entitled Apparatus and Method for Controlling the Connection and Disconnection Speed of Downhole Connectors, which is hereby incorporated by reference for all purposes. Further disclosure regarding downhole connections can be found in U.S. Patent Application Publication 2012/0181045, to Thomas, entitled Apparatus and Method for Controlling the Connection and Disconnection Speed of Downhole Connectors, which is hereby incorporated by reference for all purposes.
Additionally, wet-mate connections or wet-connects have become prevalent, especially in off-shore deep wells where it is difficult to provide for a dry-connection. A downhole communication line and a connector are often left in place, such as at the upper end of a completion string or production string. A second tool string is later lowered into the wellbore, also having a communication line and connector. The communication connectors are mated to provide an operable communication link between the tools. While it is possible to lower tool strings with all of the communication lines and corresponding conduits in place, there is increasing interest in wet-connect or wet-mate capabilities, that is, connections made in a wet environment. Further, it is often necessary or desirable to disconnect the tools and repeat the process, as later tools are inserted into the well, to speed and simplify equipment changes, replacement, or employ different tool configurations over time.
Typically wet-connects are hydraulic or electric in nature, where a pressure-competent connection or an electrically isolated connection, respectively, must be created. These require a reasonably high degree of cleanliness and several methods are known to make these connections with varying success. With the increase in usage of fiber optic communication lines in particular, it has become critical to provide an especially “clean” connection between mating connectors. Fiber optic connections generally require relatively greater positional registration and cleanliness.
Therefore, a need has arisen for apparatus and methods for wet-connecting optical fibers and other communication lines in a subterranean wellbore environment.